Widely replicated studies demonstrate that sleep can enhance memory consolidation. Potential clinical applications of such findings have only begun to be explored. We have recently shown that nocturnal sleep following simulated exposure therapy for Specific Phobia (spiders) reduced both psychophysiological and self-reported reactivity when participants were re-exposed to the same and to novel spider stimuli. The proposed research will extend these findings to a more debilitating and clinically important anxiety disorder, Social Anxiety Disorder. We will examine whether post-exposure naps can be used to strengthen therapeutic extinction memories formed during exposure exercises used in the behavioral treatment of this disorder. A total of 32 individuals with diagnosed DSM-IV Social Anxiety Disorder will be enrolled in an exposure-based group treatment for this disorder. Eight successive therapy groups of 4 patients each will be offered during the 2-year funding period. The third and fourth sessions of this validated 5-week/5-session treatment will involve each participant delivering a speech on a topic individually chosen to elicit significant social anxiety Following both of these sessions, all 4 participants will go to the nearby Massachusetts General Hospital sleep laboratory where 2 will be given a 2-hour sleep opportunity with polysomnographic (PSG) monitoring and the other 2 will be similarly instrumented but undergo 2 hours of monitored quiet wakefulness (prior to session 3 participants will be randomized to the sleep or wakefulness arm). Before beginning treatment and within several days following the final treatment session, all participants will be individually assessed for social anxiety symptoms using standardized self-report instruments. At these same times, they will undergo a Trier Social Stress Test (TSST) modified for continuous psychophysiological monitoring that also includes repeated Subjective Units of Distress (SUDS) self report and sampling for salivary cortisol. In addition to laboratory PSG, ambulatory monitoring of home sleep with actigraphy and sleep diaries will take place at pre-treatment baseline and during the last 3 weeks of treatment. We hypothesize that those individuals allowed a 2-hour sleep opportunity following exposure sessions, compared to those who remained quietly awake, will show greater questionnaire- based clinical improvement as well as lesser psychophysiological and SUDS reactivity during the modified TSST. We further hypothesize that characteristics of sleep quality and architecture during naps, specifically durations of total sleep, REM sleep and slow-wave sleep as well as REM continuity, will predict clinical improvement and diminished TSST reactivity in those who napped. To help ensure that observed sleep effects are attributable to the two 2-hour sleep opportunities, we will control for actigraph and diary-measured sleep quality during treatment. Positive results will provide the first proof-of-principle for sleep augmentation of exposure therapy for a clinically significant anxiety disorder.